Now you have seen a number of water source pollution, but I still have you to know that among the various water sources pollution in our life, one of the most incredible one is “chlorine” pollution in tap water.
“Chlorine originally does not belong to the part of water. In order to eliminate pollutants and bacteria in the water, two chlorine disinfections processes are carried on tap water in many countries. The first process of chlorination acted on water when entering into the water pant, mainly for the removal of ammonia and plankton in the water. The purpose of the second chlorination is to prevent tap water from being infected in the pipe. The disinfections method of chlorination in water was first seen in the United States in 1908, because chlorine can penetrate cell wall and react with enzymes to undermine its function, so as to achieve sterilization effect. Chlorination in the water has avoided a lot of water-borne diseases, and become a major public health hero, but 1972; the Dutch scientific community has made a observation that the combination of chlorine with organic compounds in the water can produce new compounds called “total trihalomethanes (THMs)”, but the Dutch did not have a clear description that THMs may do serious harm to human body.
In 1974, the U.S. Dr. Robert Harris pointed out in his research that the combination of chlorine with organic compounds in the water can produce the carcinogenic trichloroethane. The Japanese Dr. Tadashi Kubo also said that the ingestion of THMs in a large amount would not only induce cancer cells but also damage the central nervous system, liver function, kidney function. The study of Professor Wu Kunyu of China Medical College also showed that the volatile carcinogen such as chloroform, carbon tetrachloride and so on contained in tap water could be inhaled into the body through the lungs during the shower. These reports are indeed very alarming, because before that, no one has believed that the chlorine used to maintain the safety of drinking water has actually become a major health killer duo to its derivatives.
The water pollution crisis happened in Hong Kong is actually far away serious than we imagine and the most serious problems are the source water turbidity, E. coli, ammonia, nitrogen, iron and heavy metals pollution such as manganese, arsenic, etc. To purify these sources of pollution so that the water can meet the drinking standard, chlorine coagulant or disinfectants must be added into water, so new problems appear. In 83rd year of the Republic Of China (1994), the report on water source of water treatment plant released by the Environmental Protection Department has pointed out that part of the tap water contained human carcinogen and mutagenic substances, and it may be related with THMs produced during raw water chlorination.
In fact, chlorination may be the most convenient way for water treatment in Water Supply Company at present, but it may not be the most appropriate one. Now water purification plants have replaced chlorine with ozone for water disinfections in some countries. Although the ozone may not bring chlorine compounds, and the disinfections power of ozone is 600 to 3000 times than that of chlorine, its persistence is weak. Unless the distribution system is entirely efficient, the effect will be greatly reduced. It appears that before the new disinfections method has been developed, we’d better take our own care and hope for the best of it.
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